What is the Difference Between Azathioprine and 6-Mercaptopurine?

Azathioprine and 6-mercaptopurine, also known as 6-MP, are chemically closely related immunosuppressive drugs that are thought to reduce inflammation by blocking the immune system. They are both thiopurines and work in a similar way, with azathioprine being converted to mercaptopurine in the body. However, there are some differences between the two medications:

1. Tolerability: Some people who cannot tolerate azathioprine due to side effects may still be able to take mercaptopurine.
2. Brand Names: Azathioprine is occasionally referred to by the brand name 'Imuran', while mercaptopurine is occasionally called 'Puri-nethol' or '6-MP'.
3. Conversion: Once absorbed into the plasma, 88% of azathioprine is converted to 6-mercaptopurine.
4. Efficacy: In some cases, such as in ulcerative colitis, no significant difference between azathioprine and 6-mercaptopurine could be examined due to the limited number of studies and their designs. However, in Crohn's disease, azathioprine or 6-mercaptopurine therapy was possibly better than placebo in achieving clinical remission or improvement.

In summary, azathioprine and 6-mercaptopurine are closely related immunosuppressive drugs with similar mechanisms of action. However, they differ in their tolerability, brand names, conversion rates, and efficacy in specific conditions. Some patients may be able to tolerate one medication but not the other, and the choice between the two may depend on individual factors and the condition being treated.

Comparative Table: Azathioprine vs 6-Mercaptopurine

Here is a table comparing the differences between azathioprine and 6-mercaptopurine:

Both azathioprine and 6-mercaptopurine are thiopurine drugs used in the treatment of inflammatory bowel disease (IBD) and have been shown to be effective in inducing steroid-free clinical remission. However, their mechanisms of action differ, with azathioprine inhibiting purine synthesis and 6-mercaptopurine interfering with normal metabolic processes within cells. Additionally, the bioavailability of azathioprine is enhanced compared to 6-mercaptopurine. The therapeutic benefits of both drugs have been shown to correlate with the concentration of 6-thioguanine nucleotides in patients.